The primary efficacy objective is to evaluate whether the incidence of microembolic signals (MES) can be reduced in patients with symptomatic carotid artery stenosis who have been treated with Revacept plus antiplatelet monotherapy (aspirin or clopidogrel) versus antiplatelet monotherapy alone (placebo). MES will be assessed by transcranial Doppler (TCD) examination.

The primary efficacy objective is to evaluate whether the incidence of preoperative microembolic signals (MES) can be reduced in patients with symptomatic carotid artery stenosis who have been treated with Revacept plus antiplatelet monotherapy (aspirin or clopidogrel) versus antiplatelet monotherapy alone (placebo) prior to carotid endarterectomy (CEA). MES will be assessed by transcranial Doppler (TCD) examination.

Patients receive a single dose of trial medication by intravenous infusion for 20 minutes. The primary endpoint (MES 24 hours after treatment) is assessed. Patients are followed up one and three days after treatment, at 3 months and by a telephone interview at 12 months.

Lesions with ≥ 50 % stenosis according to the European Carotid Surgery Trial (ECST) criteria

MES detected by TCD (greater than or equal to 1 MES per hour)

Ipsilateral TIA, amaurosis fugax or stroke within the last 30 days

Age and sex: Men and women aged > 18 years Women of childbearing potential (WOCBP) must be using an adequate method of contraception to avoid pregnancy throughout the study and for up to 4 weeks after receiving investigational product in such a manner that the risk of pregnancy is minimised.

Exclusion Criteria:

Sex and reproductive Status:

WOCBP who are unwilling or unable to use an acceptable method to avoid pregnancy for up to 4 weeks after receiving investigational product.

Women who are pregnant or breastfeeding

Women with a positive pregnancy test on enrollment or prior to investigational product administration.

History of hypersensitivity, contraindication or serious adverse reaction to inhibitors of platelet aggregation, hypersensitivity to related drugs (cross-allergy) or to any of the excipients in the study drug

History or evidence of thrombocytopenia (<30.000/ul), bleeding diathesis or coagulopathy (pathological international normalised ratio (INR) or activated partial thromboplastin time (aPTT))

Thrombolysis within the last 48 hours

Relevant haemorrhagic transformation as determined by CT, NMR or anamnesis

Oral anticoagulation or other anti-platelet therapy than aspirin or clopidogrel within the last 3 weeks (3 days for dipyridamole extended release; 8 hours for tirofiban/Aggrastat)

Oral anticoagulation or dual antiplatelet therapy (aspirin combined with clopidogrel or other P2Y inhibitors) at screening; dipyridamole extended release within last 3 days; tirofiban/Aggrastat within the last 8 hours